1. Technical Field
Example embodiments of the present invention relate in general to copyright protection technology, and more particularly, to an apparatus and method for forensic marking of digital content that can be applied to multimedia content provided by an online service provider (OSP).
2. Related Art
Due to the development of information and communications technology and digital devices, demands for digital content are explosively increasing. However, most pieces of movie or music content are being illegally shared through OSPs, and thus copyright infringement is significantly increasing. According to an investigation of the Korean Film Council (KOFIC) (using data from December 2007), illegal downloading is so widespread that 47.3% of Koreans have performed illegal downloading.
Also, with the advent of the Web2.0 era, consumers who have merely consumed digital content are being developed into active producers through user created content (UCC), and cases of using a movie or drama, which is an existing work, in this process are drastically increasing. According to 2006 investigation results of the Copyright Protection Center, 84% of UCC corresponds to copyright infringement.
To prevent such copyright infringement of digital content, the government has amended copyright laws to strengthen control, and also caused OSPs to cope with copyright infringement through technical protection action. For this reason, OSPs apply forensic marking technology to digital content as a part of the technical protection action.
Forensic marking technology involves inserting information about a seller, copyright holder, or purchaser in digital data such as an image or sound source, and enables extraction of the previously-inserted information even when a user transforms digital content into another form for a dishonest purpose.
For example, when an OSP provides digital content, the OSP may insert information about a purchaser in the content using forensic marking technology. In this case, when a copyright infringement occurs later, it is possible to track and accuse an initial distributor of the content, and improve the sense of citizenship regarding copyright protection.
Unlike conventional digital rights management (DRM) technology that can only be used in a specific device or authenticated single device, forensic marking technology can be freely used in all devices and modified or processed according to a personal purpose, thus not limiting the use right of users.
However, a process of inserting a forensic mark in digital content involves decoding the entire content, inserting the forensic mark, and encoding the content again, thus requiring a considerable amount of calculation and much time.
When digital content is downloaded from an OSP via a high-speed communication network used in general homes, it takes a very short time, that is, downloading is completed within several seconds to several minutes. On the other hand, as mentioned above, it takes a long time to insert a forensic mark in digital content. Thus, if a forensic mark is inserted when a request of a purchaser is received, a service delay occurs. Currently-served content in which a forensic mark has been inserted is generated before a request of a purchaser is received, and thus does not include information about a purchaser or content transmission time.
To solve this problem, Korean laid-open patent publication No. 2009-79045 (Method and Apparatus for Realtime-Providing Multimedia Contents Comprising Watermark) discloses a method of preparing multimedia content in which a watermark has been inserted before a request of a user is received, relating an identification (ID) of a user with an ID of the multimedia content in which the watermark has been inserted, and then providing the content when a request of the user is received.
However, in Korean laid-open patent publication No. 2009-79045, a very large storage space is required to store content that is frequently requested for purchase because pieces of the same content have different watermark values, and a storage space is wasted or content cannot be provided when demand forecasting is wrong. Also, instead of information about a purchaser being directly inserted in a watermark value, an ID having no meaning is inserted. Thus, to track down the original purchaser of illegally-shared content, a matching table between a content purchaser and an ID should be provided by each OSP.